This research will examine the influence of prenatal and early life experiences on the adaptive capacity of animals as reflected in the development of behavioral and physiological processes, adult behaviors, and physiological reactivity, and in susceptibility to potentially pathogenic stimulation. Accomplishing these aims will necessitate a further definition of the several situations to be used in the manipulation of experiential history and in the assessment of the effects of these manipulations. More generally, we will study the effects of prenatal maternal experiences and early life experiences (including mother-young interactions) on the development of behavioral rhythmicity (activity) and Physiological rhythmicity adrenocortical function), adult behaviors such as emotional reactivity, passive avoidance and illness-induced taste aversion, and susceptibility to experimentally-induced gactric lesions.